U.S. patent application number 13/919082 was filed with the patent office on 2014-04-10 for deflection spring pneumatic actuator.
This patent application is currently assigned to TSE BRAKES, INC.. The applicant listed for this patent is TSE BRAKES, INC.. Invention is credited to CARL GAUFIN.
Application Number | 20140096677 13/919082 |
Document ID | / |
Family ID | 48703141 |
Filed Date | 2014-04-10 |
United States Patent
Application |
20140096677 |
Kind Code |
A1 |
GAUFIN; CARL |
April 10, 2014 |
DEFLECTION SPRING PNEUMATIC ACTUATOR
Abstract
A pneumatic actuator includes a housing defining a chamber. A
diaphragm is positioned within the chamber. A rod member is
attached to the diaphragm and is movable between a first position
and a second position. A cam member is attached to the diaphragm
and to the rod member. The cam member has a cam surface. A
deflection rod has a first end portion and a second end portion,
where the first end portion of the deflection rod is attached to
the housing A follower is attached to the second end portion of the
deflection rod. The follower engages the cam surface of the cam
member so as to time the rod member towards the second
position.
Inventors: |
GAUFIN; CARL; (Cullman,
AL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TSE BRAKES, INC. |
CULLMAN |
AL |
US |
|
|
Assignee: |
TSE BRAKES, INC.
CULLMAN
AL
|
Family ID: |
48703141 |
Appl. No.: |
13/919082 |
Filed: |
June 17, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61660131 |
Jun 15, 2012 |
|
|
|
Current U.S.
Class: |
92/63 |
Current CPC
Class: |
B60T 17/083 20130101;
F16D 2123/00 20130101; F16D 2121/08 20130101; F16D 2121/10
20130101; F15B 15/02 20130101; F16D 65/28 20130101 |
Class at
Publication: |
92/63 |
International
Class: |
F15B 15/02 20060101
F15B015/02 |
Claims
1. A pneumatic actuator comprising: a) a housing defining a
chamber; b) a diaphragm positioned within the chamber; a rod member
attached to the diaphragm, said rod member movable between first
position and a second position; d) a cam member attached to the
diaphragm and to the rod member, said cam member having a cam
surface; e) a deflection rod having a first end portion and a
second end portion, there the first end portion of the deflection
rod is attached to the housing; f) a follower attached to the
second end portion of the deflection rod, said follower engaging
the cam surface of the cam member so as to urge the rod member
towards the second position.
2. The pneumatic actuator of claim 1 wherein the rod member is a
push rod.
3. The pneumatic actuator of claim 1 wherein the cam surface is a
convex hemispherical cam surface.
4. The pneumatic actuator of claim 1 wherein the cam member is
cup-shaped.
5. The pneumatic actuator of claim 4 wherein the cam surface is a
concave annular cam surface.
6. The pneumatic actuator of claim 1 wherein the follower is fixed
to the end of the deflection rod.
7. The pneumatic actuator of claim 1 wherein the follower includes
a roller rotatably attached to the end of the deflection rod.
8. The pneumatic actuator of claim 1 wherein the rod member
includes a sleeve adapted to receive an end portion of an actuator
rod.
9. The pneumatic actuator of claim 1 wherein the housing includes a
cap having a recess and wherein the first end portion of the
deflection rod is positioned within the recess.
10. The pneumatic actuator of claim 1 wherein the housing includes
a cylindrical shaped portion and the cam member includes an annular
groove with an O-ring positioned therein, said O-ring forming a
circumferential seal between the cam member and the housing.
11. A deflection spring, assembly for a pneumatic actuator having a
housing and a rod member that is movable between a first position
and a second position comprising: a) a cam member adapted to be
attached to the rod member, said cam member having a cam surface;
b) a deflection rod having a first end portion and a second end
portion, where the first end portion of the deflection rod is
adapted to be attached to the housing; c) a follower attached to
the second end portion of the deflection rod, said follower adapted
to engage the cam surface of the cam member when the cam member is
attached to the rod member and the first end of the deflector rod
is attached to the housing so as to urge the rod member towards the
second position.
12. The deflection spring assembly of claim 11 wherein the rod
member is a push rod.
13. The deflection spring assembly of claim 11 wherein the cam
surface is a convex hemispherical cam surface.
14. The deflection spring assembly of claim 11 wherein the cam
member is cup-shaped.
15. The deflection spring assembly of claim 14 wherein the cam
surface is a concave annular cam surface.
16. The deflection spring assembly of claim 11 wherein the follower
is fixed to the end of the deflection rod.
17. The deflection spring assembly of claim 11 wherein the follower
includes a roller rotatably attached to the end of the deflection
rod.
18. The deflection spring assembly of claim 11 further comprising a
sleeve attached to the cam member and adapted to receive an end
portion of an actuator rod.
19. The deflection spring assembly of claim 11 further comprising a
push rod integrally formed with the cam member.
20. The deflection spring assembly of claim 11 wherein the housing
includes a cylindrical-shaped portion and the cam member includes
an annular groove with an O-ring positioned therein, said O-ring
forming a circumferential seal between the cam member and the
housing.
Description
CLAIM OF PRIORITY
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/660,131, filed Jun. 15, 2012, the contents of
which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to air brake systems
for vehicles and, in particular, to a deflection spring for the
pneumatic actuator of such a system.
BACKGROUND
[0003] Heavy trucks, trailers and other commercial vehicles
typically use an air brake system to provide the braking forces
necessary to stop the vehicle. Such a system typically includes a
brake pedal positioned on the floor of the driver's cab or
compartment of the vehicle that, upon actuation, provides air from
an air reservoir to an air chamber. The air chamber acts as a
pneumatic actuator in that it features an actuator rod that either
extends out of or retracts into the air chamber so as to activate
the mechanism that pushes the brake lining material of the brake
shoes against the vehicle brake drum at each vehicle wheel-end. The
mechanism typically includes a slack adjustor which turns a cam
roller via a camshaft so as to force the brake shoes to engage the
brake drum so as to stop the vehicle.
[0004] An example of a prior art pneumatic or air chamber of such
an air brake system is described in U.S. Pat. No 5,829,339 to
Smith, the contents of which are hereby incorporated by
reference.
[0005] Cross-sectional views of a prior art air chamber are also
provided in FIGS. 1A-1D. As explained in greater detail below, with
reference to FIGS. 1A-1D, a large main compression spring 10 also
known as a parking spring or a power spring) serves as a mechanical
means to prevent the vehicle from rolling when there is no air in
the brake system and when the vehicle is stationary or parked. This
spring supplies the parking force needed to hold the vehicle
stationary. A larger or stronger spring typically means that a
larger parking force can be achieved.
[0006] One problem with such a design is that a great deal of air
pressure is needed to keep the main spring from applying the brake
and thereby maintain the spring in a compressed state (illustrated
in FIG. 1A). Also as the brake applies and the main spring 10
extends (as illustrated in FIG. 1C), one is not able to capitalize
on the high amount of force that the spring exhibits in the
compressed state (due to the equation Spring Force=K.times.X, where
K is the spring constant and X is the compression distance of the
spring). To this end, the main spring is subjected to very high
compressive forces when in the condition of FIGS. 1A, 1B and 1D
that are never translated to the parking brake force for the
vehicle.
[0007] In addition, while in the compressed state (FIG. 1A) the
main spring coils are close together and could be touching. This
contact, combined with the vibrations experienced by the axle and
vehicle as it drives, could cause an increase in wear in the spring
coils. This wear could possibly break through the spring plating
and damage the spring surface creating high stress areas and,
without a protective coating, the spring would be subject to
corrosion. The resulting rust pits become stress risers that will
shorten the life of the spring.
[0008] A coil spring failure can result in a punctured diaphragm or
a reduction in stroke, parking force, or the inability to
completely release a brake for a given wheel-end of the vehicle. As
such, much work must be put into protecting the spring from
corrosion and also from individual coil contact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIGS. 1A-1D are cross-sectional views of a prior art air
chamber or pneumatic actuator with the parking chamber pressurized,
both the parking and service chambers pressurized, the main spring
engaged (with neither the parking nor the service chambers
pressurized) and the main spring mechanically caged with a release
tool, respectively;
[0010] FIGS. 2A and 2B are cross-sectional views of a pneumatic
actuator according to a first embodiment of the invention showing
the deflected and non-deflected spring conditions,
respectively;
[0011] FIGS. 3A and 3B are cross-sectional views of the top portion
of an air chamber equipped with a second embodiment of the
deflection spring of the invention showing the deflected and
non-deflected spring conditions, respectively;
[0012] FIGS. 4A and 4B are cross-sectional views of a top portion
of an air chamber equipped with a third embodiment of the
deflection spring of the invention showing the deflected and
non-deflected spring conditions, respectively:
[0013] FIG. 5 is an enlarged perspective view of the cam member and
push rod of FIGS. 2A and 2B and 3A and 3B;
[0014] FIG. 6 is an enlarged perspective view of the cup-shaped cam
member and central sleeve of FIGS. 4A and 4B;
[0015] FIG. 7 is a graph of a force curve illustrating the parking
force provided by a prior art main spring;
[0016] FIG. 8 is a graph of a force curve illustrating the parking
force provided by an embodiment of the deflection spring of the
invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0017] As noted above, FIGS. 1A-1D provide cross-sectional views of
a prior art air chamber or pneumatic actuator, indicated in general
at 12. While the invention is described in terms an air chamber for
an air brake system of a vehicle, it is to be understood that the
deflection spring of the present invention may be used in other
types of pneumatic actuators for a variety of purposes.
[0018] The air chamber includes an actuator rod 14 and a housing 16
that defines a parking chamber 18 and a service chamber 20 (FIGS.
1A, 1C and 1D). The bottom end of the actuator rod is connected to
a lever arm 22 that attaches the actuator rod to a slack adjustor
or a camshaft upon which the cam roller (for actuating the brake
shoes) is positioned. An upper diaphragm 24 is positioned within
the parking chamber while a lower diaphragm 26 is positioned in the
service chamber. The main compression spring 10 is positioned
between an upper plate 30, which is mounted to the top end of a
push rod 32 (FIGS. 1C and 1D) and the upper diaphragm, and the top
of the housing 16. A lower compression spring 34 is mounted between
a lower plate 36, which is mounted to the top end of the actuator
rod and the lower diaphragm, and the bottom of housing 16. A
chamber divider wall 38 positioned within the housing separates the
parking and service chambers and has a central opening 40 through
which the push rod 32 passes. An upper compression spring 44 (FIG.
1D) is positioned between the top of the chamber divider wall 38
and the bottom of upper diaphragm 24 and upper plate 30.
[0019] In operation, as illustrated in FIG. 1A, when parking
chamber 18 is pressurized, upper diaphragm 24, upper plate 30, push
rod 32, lower diaphragm 26 and lower plate 36, and thus the
actuator rod 14, move upwards, as indicated by arrow 46. This
causes main spring 10 to be compressed, while the upper and lower
springs extend. As a result, the vehicle brakes are released and
the vehicle may be driven. When the vehicle driver presses down on
the vehicle brake pedal, the service chamber is pressurized, as
illustrated in FIG. 1B. This cause the lower diaphragm 26 to move
down and the lower spring 34 to be compressed. As a result,
actuator rod 14 moves down, as indicated by arrow 48, and the
vehicle brakes are applied.
[0020] The situation when the vehicle is off or air is otherwise
evacuated from the air brake system is illustrated in FIG. 1C. When
this occurs, air is absent from the parking and service chambers 18
and 20 and the main spring 10 pushes the push rod 32 and actuating
rod 14 downward in the direction of arrow 52 so that the vehicle
brakes are applied. As illustrated in FIG. 1D, the actuating rod
may be raised, as indicated by arrow 54, and the main spring
mechanically caged, through use of a release tool so that the
vehicle may be moved even though there is no air in the vehicle
brake system.
[0021] In accordance with the present invention, the main spring 10
of FIGS. 1A-1D is replaced With a deflection spring assembly. More
specifically, in accordance with the present invention, a pneumatic
actuator, indicated in general at 100 in FIGS. 2A and 2B, includes
a number of deflection beams or rods 102a-102d. While four
deflection rods are illustrated, an alternative number
advantageously (as explained below) could be used.
[0022] In addition to the deflection rods 102a-102d, the deflection
spring assembly, indicated in general at 103, includes a cam member
101 having a convex hemispherical cam surface 104 (FIGS. 2A, 2B and
5) positioned on top of, and connected to or otherwise provided
with, a push rod 105 and upper diaphragm 124 (which corresponds to
upper diaphragm 24 of FIGS. 1A-1C). Furthermore, the bottom ends of
the deflection rods 102a-102e are provided with followers 106a-106d
that engage and travel along the cam surface 104. The followers
preferably feature a disc-shaped construction and are attached to
the ends of the deflection rod. The followers may he mounted to the
ends of the deflection rods in a fixed fashion, being either
integrally formed with the deflection rods (as illustrated in FIGS.
2A and 2B) or independently formed and joined to the rods.
[0023] The deflection springs and associated components of FIGS. 2A
and 2B are positioned within a parking chamber housing 116 that
features top cap 117. The parking chamber housing also includes a
port 115 (FIG. 2A) through which pressurized air may selectively be
introduced into the parking chamber from a pressurized air source,
such as the air brake system of a truck. As illustrated in FIGS. 2A
and 2B, the top cap features a number of recesses 119 that receive
the top ends of the deflection rods 102a-102d. The forces acting on
the deflection rods 102a-102d (explained below) keep the top ends
of the deflection rods within the recesses of top cap 117, and/or
they may be secured in place with adhesive, welding or some other
fastening arrangement.
[0024] The remaining components of the pneumatic actuator 100 of
FIGS. 2A and 2B are similar to the components of the pneumatic
actuator of FIGS. 1A-1D and function in the same manner. The
parking chamber housing 116 defines a parking chamber 118, while a
service chamber housing 121 defines a service chamber 120. The
service chamber housing is provided with a port 123 (FIG. 2B)
through which pressurized air may be selectively introduced into
the service chamber from a source of pressurized air, such as the
air brake system of a vehicle. The bottom end of an actuator rod
114 is connected to a lever arm (not shown) of a braking system.
The upper diaphragm 134 is positioned within the parking chamber
while a lower diaphragm 126 is positioned in the service chamber. A
lower compression spring 134 is mounted between a lower plate 136,
which is mounted to the top end of the actuator rod 114 and the
lower diaphragm, and the bottom of the service chamber housing 121.
A divider wall 138 separates the parking and service chambers and
has a central opening through which the push rod 105 passes. An
upper compression spring 145 is positioned between the top side of
the divider wall 138 and the bottom of upper diaphragm 124 and the
cam member 101.
[0025] In an alternative embodiment, illustrated in FIGS. 3A and
3B, three followers 206a-206c are mounted upon three deflection
rods 202a-202c. In this embodiment, the followers take the form of
spherical rollers that pivot, rotate or otherwise turn about an
axle as illustrated at 208 for follower 206c) with respect to the
bottom ends of the deflection rods. Alternatively, the spherical
followers may be mounted to or integrally formed with the
deflection rods in a fixed fashion as illustrated by follower
206a). In the embodiment of FIGS. 3A and 3B, the deflection springs
and associated components are positioned within an air chamber
housing 216. The top ends of the deflection rods 202a-202c are
mounted in such a way that they rest inside a recess or recesses
formed within the inner surface of the top of the housing 216,
deformations (218) or an annular projection or ridge formed in or
on the interior surface near the center of the top of the housing.
The resulting forces keep the top ends of the deflection rods in
place within the housing. Alternatively, the top ends of the
deflection rods may be mechanically fastened or joined to the
housing using, as examples, only, a fastener, such as a screw or
bolt (209 in FIG. 2A), adhesive or welding. In addition, in the
embodiment of FIGS. 3A and 3B, the push rod 205 is integrally
formed with the cam member 201, which has a convex hemispherical
cam surface 204 (like cam member 101 of FIGS. 2A, 2B and 5).
[0026] In yet another alternative embodiment of the invention,
illustrated in FIGS. 4A and 4B, the cam member having a
hemispherical cam surface of FIGS. 2A and 2B is replaced with a
cup-shaped cam member 220 (also shown in FIG. 6) having walls with
internal surfaces that form a concave annular cam surface 222. The
cup-shaped cam member has a central sleeve 223 that acts as a push
rod (32 of FIGS. 1A-1D) and receives the top end of the actuator
rod (225 in FIG. 4A). Similar to the embodiment of FIGS. 2A and 2B,
deflection rods 132a-132c are provided with followers 234a-234c
which are shaped to engage and travel along the concave annular cam
surface 222 of the cup-shaped cam member 220. While three
deflection rods are shown, an alternative number may advantageously
be used. In addition, while the followers 234a-234c are shown as
fixed to the bottom ends of the deflection rods 232a-232c, they
alternatively may take the form of rollers, as illustrated for
follower 206c in the embodiment of FIGS. 3A and 3B. The housing 226
of the air chamber features a central recess 236 that limits the
upwards travel of the cup-shaped cam member 220. In this
embodiment, the cup-shaped cam member 220 seals against the
interior surface of the sides of the cylindrical housing 226 via
O-rings 237a and 237b (illustrated in phantom in FIG. 4B)
positioned in annular grooves 239a and 239b (also shown in FIG. 6).
As a result, the cup-shaped cam member 220 serves as the upper
diaphragm for the assembly so that the separate upper diaphragm 124
in the embodiment of FIGS. 2A and 2B (or 24 of FIGS. 1A-1D) is not
required.
[0027] The top ends of the deflection rods 232a-232e are mounted in
such a way that they rest inside an annular recess or recesses
(238a-238c), deformations or an annular projection or ridge formed
in or on the interior surface near the periphery of the top of the
housing. The resulting forces keep the top ends of the deflection
rods in place within the housing. Alternatively, the top ends of
the deflection rods may be mechanically fastened or joined to the
housing.
[0028] In operation, the deflection rods resist the deflected
condition illustrated in FIGS. 2A, 3A and 4A so that the cam
surface, and thus the push rod, is urged downward into the
positions illustrated in FIGS. 2B, 3B and 4B. FIGS. 2A, 3A and 4A
correspond to the brake system configurations of FIGS. 1A, 1B and
1D, while FIGS. 2B, 3B and 4B correspond to the brake system
configuration of FIG. 1C.
[0029] In choosing the size of followers 106a-106d (FIGS. 2A and
2B), 206a-206c (FIGS. 3A and 3B) or 234a-234c (FIGS. 4A and 4B),
one must keep in mind that with a static system, any spherical
object with an applied force on it has a resulting force through
the centroid of the sphere and normal to the plane or surface
(convex cam surface 104 of FIGS. 2A and 2B, convex cam surface 204
of FIGS. 3A and 3B or concave cam surface 222 of FIGS. 4A and 4B)
that is touching it. With this in mind, it is important to choose
an appropriate size spherical or dome-shaped contact that will
allow the attaching rod or beam (deflection rods) to not contact
the cam surface such that the resulting free body diagrams can be
simplified.
[0030] When the follower (sphere or dome-shaped surface) and
deflection rod are in their resting state (no deflection), there is
no horizontal force component and everything is in the vertical
direction. As this is not a stable condition, the sphere and rod
are installed such that there is a slight deflection of the
deflection rods when in the condition of FIGS. 2B, 3B and 4B
thereby assuring the proper direction of travel. The resulting
small horizontal force is relatively negligible in comparison to
the vertical component.
[0031] As the cam surface moves upward between the positions of 2B
and 2A, 3B and 3A or 4B and 4A, thereby releasing the brake, the
vertical force component of the roller against the cam surface gets
smaller and smaller while the horizontal component gets larger and
larger. Care must be taken to not pass the point where all of the
force goes to the horizontal components as this would be another
unstable condition and the cam surface could then continue up and
then the beam and sphere assembly would he physically holding the
brake off.
[0032] The embodiment of the invention described above therefore
takes advantage of the deflection of a beam or rod and the
resulting horizontal and vertical force components seen by a cam
surface and a follower type of contact. These deflection rods or
beams produce a vertical or applied force curve that is the inverse
of the current spring design, as illustrated in FIGS. 7 and 8 where
the spring curves of a prior art coil compression spring and an
embodiment of the deflection spring of the invention are
illustrated, respectively. As a result, the more distance the
actuator rod travels downward (so as to drop or extend) in the
embodiments of FIGS. 2A-6, the stronger the deflection spring force
(FIG. 8) gets, as opposed to the prior art compression coil spring
which loses force (FIG. 7) the more the actuator rod drops or
extends. In addition, when the brake is released (FIGS. 2A, 3A and
4A), the vertical force required to hold off the brake is minimal
as most of the force components exerted by the followers on the cam
surface are now in the horizontal direction.
[0033] The use of deflection rods or beams also enables one to
better control the desired force output of the unit by simply
adding or removing deflection rods. Corrosion of the spring is not
as relevant as the preferred deflection rod material includes
carbon fiber or aramid reinforced materials, which exhibit high
tensile strengths and flexibility. Other materials that exhibit at
least a semi-elastic behavior may be alternatively used. By using
an embodiment of the deflection spring of the invention, there is
also a possibility of reducing the overall weight of the air
chamber, which lowers the amount of stress seen by the mounting
bolts.
[0034] While the preferred embodiments of the invention have been
shown and described, it will be apparent to those skilled in the
art that changes and modifications may be made therein without
departing from the spirit of the invention, the scope of which is
defined by the appended claims.
* * * * *